Well, I was getting so tired of the dreaded NV5600 hard shifting that I took matters into my own hands.
A mechanic friend pointed out to me that all of the big truck trannies take 75-90 or 80-90, so I change my water - 5w30 out to some XP 75w90. Within two days I noticed a difference. Now after 15k, it shifts pretty close to normal. Cold days are a bit tougher at first till it warms up, but after that it's good to go....... I wish that I had done this years ago, I bet having that runny crap in there has caused damage.

Anyway, I just thought I would pass that on. Do as you will, this is only my .02 and what I am doing.

 

I hope it's GL-4 rated fluid and not GL-5. GL-5 spec fluid is hard on soft metals.

Did you try sythetic Redline MTL or Amsoil MTF?

MikeyB

 

Goodbye synchros? Doing a lot of cross reference on the NV5600 led me to believe shifting difficulties stemmed from insufficient oil levels. The filler port on the side is too low and the proper level is the upper bolt on the PTO cover. At -20F, my NV5600 so filled with factory Mopar stuff shifts superbly, right out of the driveway. That said, I'm trying Amsoil next because it's half the price and a synthetic to boot.

The NV5600 and NV3500 are unique in that they require a special light weight synchomesh oil. Differential oil is definitely bad news.

Read, read, read a lot on here and TDR before jumping to the wrong conclusion.

 

I'm going to Amsoil myself. I'll try that "top bolt" theory and report back. We all know the NV5600 is strong but shifts horribly.

 

Not mine, or dads, both have reline mtl, both shift great. At -30 or 90 above

 

I think the NV5600 is a strong trans.But its the worst shifting thing I've ever driven except a old Fiat(it was OLD back in 1971)with a 4 speed on the column.Amsoil improved it over factory fill but Amsoil can't fix a bad design!

 

I'm using Amsoil in it, if it goes bye bye, so be it. It's either get the shifting working better or get rid of the truck and get a Duramax.

I did a lot of reading, talked to everyone and their cousin, had two dealerships look at it, one of them two times. I upgraded to a Southbend HD hydraulic system, tried a couple types of 5w30s and nothing helped.

Rod-M. I did the overfill thing too. All that happened was a blown out gasket. Try a 5 to 10 hr drive and see what happens. I hope yours lasts, mine didn't. After 125k of crappy shifting and tons of cash thrown at it, it's the last straw..... It's either going to work or screw up the tranny, I don't care anymore.

Have a good one all.

 

if you blew a gasket, i don't know where it was, my trans does not have any gaskets.... all mating surfaces are sealed with a silicone type sealer

 

It has front and rear seals. I dont like the way mine shifts either. Its much worse since the SB clutch, and i too went with thier upgrade hydros.

 

I'm running a 2 quart Amsoil overfill in mine, still shifts like crap!

Rick

 

Is there a real solution or just the nature of the beast. Im still adj. the sb linkage trying to get back at least were i was, no luck yet. Not as bad once rolling but at every stop it dont go in gear good at all.

 

I've got 34k on mine and it shifts fine. Not fast, but smooth and reliable. I like it much better than the auto truck (04.5) I had immediately prior.

I've only got 4k on the change of Mopar stuff, but they sucked it out and did not clean the magnet. This I'll do this weekend, was well as install the filter kit and refill with amsoil. I really don't expect any change in behavior, but we'll see. As far as a 5-10 hour drive, I guess going over the continental divide on the way to Helena might count. And then on to Townsend, Jordan, Ft Peck, and finally Malta. And back of course. About 12 hours each way all told. No problem.

 

I'm running 6 qts of Amsoil MTF in mine and shifts pretty good for the last 15k miles.

MikeyB

 

I added the last qt.(6th)a few thousand miles after the fact.It did make a differance.Took away some growl and was a hair smoother.

 

Are yall putting the extra oil in from up top-through the shifter? You said 6 quarts i thought i remember it holding only 4, your putting 2 more with it correct. Ill try something diff. for sure, at only 60,000 of good driving shouldnt have this prob. i still think most of it is clutch.